Optimization Of Solid State Fermention Conditions Of Streptomyces NEAU6 And Its Effect On The Growth Of Four Vegetables

The excessive use of pesticide and chemical fertilizer has caused serious agricultural ecological pollution and food safety problems.Microbial fertilizers with probiotics as the core can not only effectively promote crop growth and improve crop quality,but a lso has no threat to soil ecological environment.Compared with the traditional liquid fermentation process,the solid state fermentation process has the advantages of simple equipment,low cost and no pollution to environment,and it is suitable for application in the field of agriculture.Therefore,the study of bio-fertilizers that suitable for agricultural production by solid state fermentation technology will bring new opportunities for the development of agricultural industry.In the study,Streptomyces NEAU6 was used the experimental strain,and cultured by solid state fermentation.The fermentation medium was screened and the culture conditions were optimized by response surface methodology.The effect of Streptomyces NEAU6 on the growth of lettuce was studied by plate germination experiment and pots experiment.The optimum concentration of Streptomyces NEAU6 and its effect on vegetable quality and chlorophyll content were stu died by field experiment.The results will provide theoretical basis and data reference for industrial production of Streptomyces NEAU6 bio-fertilizer.The colonization ability of the strain in the rhizosphere of lettuce was also studied.At the same time,we analysised the effect of Streptomyces NEAU6 on the quantity of microorganisms in soil.Two new strains were isolated and identified by polyphasic taxonomy.The results of this study are as follows:(1)The best formulation for culture medium of Streptomyces NEAU6 were vermicompost and wheat bran with the ratio was 3:1.The solid state fermentation conditions of Streptomyces NEAU6 were optimized by response surface methodology.The inoculation amount was 10%,the water content was 70% and the temperature was 27 oC.On the 7 day,the spore amount of Streptomyces NEAU6 reached the maximum,which was 6.05×1011 CFU·g-1.(2)The germination experiment of lettuce seeds indicated that Streptomyces NEAU6 could significantly increase the bud length and root length.When the spore concentration was 5.2×106 CFU·m L-1,the bud length and root length increased by 27.78% and 14.71%,respectively.(3)The pots experiment of lettuce showed that when the spore quantity of Streptomyces NEAU6 was 6×107 CFU·g-1,the yield per plant increased by 26.0%,the plant height increased by 12.35%,the leaf length and leaf width increased by 8.00% and 15.60%,respectively,and the difference was significant compared with the control group.(4)Field experiments indicated that when the spore quantity of Streptomyces NEAU6 was 6×107 CFU·g-1,the growth-promoting effect of lettuce and chinese cabbage was significant.Compared with the control group,the yield per plant increased by 48.0 0% and 37.06%,respectively.When the spore quantity of Streptomyces NEAU6 was 6×106 CFU·g-1,the growth-promoting effect of garland chrysanthemum and coriander was significant.Compared with the control group,the yield per plant increased by 40.84% and 20.69%,respectively.(5)Streptomyces NEAU6 could colonize in the rhizosphere of lettuce.After 28 days,the quantity of Streptomyces NEAU6 was 7.13×105 CFU·g-1 in rhizosphere soil and 2.73×103 CFU·g-1 in root tissue.(6)The results showed that the effect of Streptomyces NEAU6 on soluble sugar and soluble protein in lettuce leaves was the most significant,which increased by 47.00% and 20.53%.The content of soluble sugar in leaves of garland chrysanthemum,chinese cabbage and coriander increased by 79.65%,36.32% and 46.45%.The results of chlorophyll content determination showed that Streptomyces NEAU6 significantly affected the chlorophyll content in leaves of four kinds of vegetables.The chlorophyll contents in lettuce,garland chrysanthemum,chinese cabbage and coriander increased by 51.89%,33.64%,52.14% and 38.51%.(7)Effects of Streptomyces NEAU6 on microbial population in rhizosphere soil of lettuce showed that the number of bacteria in the soil increased by 41.30%,the number of actinomycete increased by 37.32%,the number of fungi decreased by 24.64%.(8)Identification of strain NEAU-85 T and strain NEAU-YG30 T by polyphasic taxonomy,the results showed that strain NEAU-85 T belongs to the genus Cryobacterium,and strain NEAU-YG30 T belongs to the genus Nonomuraea.